In a semiconductor device, a plurality of unit elements such as transistors, bit lines, or metal wires can be integrated into a substrate. The plurality of unit elements should often be insulated from one another. An insulating film can be used to insulate the unit elements from one another, and an oxide film has been used as a typical insulating film. A BPSG (Boro Phospho Silicate Glass) film, a BSG (Boro Silicate Glass) film, a PSG (Phospho Silicate Glass) film, a TEOS (Tetra Ethyl Ortho Silicate) film, an USG (Undoped Silicate Glass) film, or a combination thereof have also been used as insulating films.
Due to a high degree of integration of the semiconductor device, a distance between patterns thereon is decreased and a height of each pattern may be increased. As a result, an aspect ratio of the pattern may be increased. When a gap is filled during the deposition of an insulating film, an increase in the aspect ratio of the gap may cause defects in the insulating material used to fill the gap.
A HDP (High Density Plasma) oxide film has been used as an insulating film having excellent gap-filling characteristics. However, since the HDP oxide film is formed by a high-density plasma, plasma attack against lower patterns (for example, gate electrode patterns) may be caused by the high-density plasma. Accordingly, a HARP (High Aspect Ratio Planarization) method has been proposed to solve problems generated when an insulating film is deposited by plasma. However, seams may be formed in a material of a HARP oxide film due to the characteristics of the deposition process. Moreover, because a wet etching rate of the HARP oxide film with respect to a hydro-fluoric acid (hereinafter, referred to as “HF”) is larger than that of the HDP oxide film, the upper surface of an element isolation film may become recessed to a large depth, thereby generating internal stress within subsequently formed integrated circuit devices.